CURIOUSLY little has been written about the electroencephalographic changes found in association with encephalitis. A report of 1 case was published by Lindsley and Cutts,1and the "Atlas of Electroencephalography"2contains figures and several references to this subject. A more extensive report was published by Ross,3but it was based on only 4 cases. Since encephalitis is a clinical condition of major importance, and since some of the most definite abnormalities that are seen in electroencephalography are encountered in patients with this condition, it seems appropriate to report on a larger number of cases. MATERIAL AND METHOD This investigation is based on 240 cases of a disorder clinically diagnosed as encephalitis, studied in different phases of the disease. Ideally it would be desirable to base such a survey on longitudinal data and on electroencephalograms prior to infection; but, for obvious reasons, this is exceedingly difficult if not